Roof expansion bolt having a flexible strap connecting shell halves for anchoring



"July 16,1957 1.1;. GENTERQ 2,799, 1

ROOF EXPANSION BOLT HAVING A FLEXIBLE STRAP CONNECTING SHELL HALVES FORANCHORING Filed Aug; 3, 1954 2 Shuts-Sheet 1 I mmvrox. ALBETH.GENTEEJuly 16, 1957 A; H. GENJTER 1- 2,799,

Filed Aug. -3, 1954 ROOF EXPANSION BOLT HAVING A FLEXIBLE STRAPCONNECTINGSHELL HALVES FOR ANCHORING v 2 Sheets-Sheet 2 uvyzurox. A 1.552 TH. 654/7542 HIS Arroeflsv United States PatentQ ROOF EXPANSION BOLTHAVING A FLEXIBLE STRAP CONNECTING SHELL HALVES FOR ANCHORING Albert H.Genter, Mount Lebanon, Pa.

Application August 3, 1954, Serial No. 447,543

1 Claim. (Cl. 852.4)

This invention relates generally to expansion shells for mine roof boltsand more particularly an improved expansion shell design.

One mode of supporting a mine roof is to drill a hole up into the roofand pass a long bolt through a plate and up into the hole with a nut andexpansion shell on the end thereof. When the bolt head engages the plateagainst the roof, the bolt is turned to draw the nut downwardly andexpand the shell outwardly to tightlyengage the sides of the hole.

Most expansion shells are formed in one integral casting being made ofone part or casting. This construction requires a core which limits themanner in which the shells are made as well as the cost of production.

One object of the present invention is the provision of an expansionshell fabricated from duplicate halves. These halves may be stamped orcast to shape and are connected by a flexible strap.

Another object is the provision of a metal strip to provide the flexiblestrap connecting the duplicate halves of the expansion shell. The stripmay be notched and locked in a slot across the ends of the expansionshell halves to flexibly hold them together. The locking can be done bypeening the sides of the slot over on the notches in the strap.

Another object is the provision of spaced notches in the strap, one foreach shell half to maintain the shell halves in spaced relation when thestrap is connected thereto at the spaced notches. This prevents thehalves from shifting relative to each other.

Another object is the provision of an abutment on each shell half toengage each other shell half and form a fulcrum point from which theshell halves expand. This abutment may extend the full width of shellhalves. If the base of each shell half is arcuate the abutments may bespaced. These spaced abutments may have a fulcrum socket on one side anda fulcrum on the other which interlock in mating relation with aduplicate shell half to form the connecting abutments.

Another object is the provision of stiff ends on the connecting flexiblestrap means to extend laterally beyond the shell halves to engage in thehole into which it is inserted to lodge the same and prevent it fromturning.

Other objects and advantages appear hereinafter in the followingdescription and claim.

The accompanying drawings show for the purpose of exemplificationwithout limiting the invention or claim thereto certain practicalembodiments illustrating the principles of this invention wherein:

Fig. 1 is a perspective view of the expansion shell comprising thisinvention.

Fig. 2 is a sectional view of the expansion shell having a nut and bolttherein.

Fig. 3 is an end view of the shell shown in Figs. 1 and 2.

Fig. 4 is a detailed view of the flexible strap.

Fig. 5 is a view in side elevation of a shell having fulcrum typeabutments.

ice

Fig. 6 is a perspective view of the structure shown in Fig. 5.

Fig. 7 is an end view of an expansion shell the abutment of whichextends across the base of the shell'half.

Referring to the drawings the expansion shell 1 shown in Figs. 1 and 2is made up of the halves 2 and 3 which are duplicates of each other.Each shell half is made up of a base section 4, a straight stem section5 and a wedging finger section 6. The finger sections have a series ofparallel ridges 7 on their outer face that form gripping surfaces.

Each of the gripping fingers increases in arcuate cross section from thestem section 5 outwardly as shown in Figs. 1 and 2 and the edges of thefingers are the spaced sliding wedge surfaces 8 and 9 on which the sidesof the nut 10 ride when it is drawn to the right in Fig. 2 and along thethreads of the bolt 11. The bolt 11 extends through a hole 12 in plate13 and the plate 13 is held tight against the roof by the head of thebolt which is turned so as to draw the nut downwardly towards the plateand thus expand the fingers 2 and 3 that are wedged in the hole by thenut which draws the bolt head tightly against the plate 13 to hold theceiling in place.

As shown in Figs. 1 to 3 the shell base sections 4 are provided witharcuate sections having abutments 14 and 15. The abutment 14 is oppositeto the abutment 15 on the opposed shell member. These abutment surfacesmay be rendered as indicated at 16 in Fig. 2 and they also may be curvedin the other dimension as illustrated at 17 in Fig. 3. These abutmentsengage each other and permit the inner ends of the shell members to beclose together while the outer fingers of the shell member extendagainst the walls of the hole.

The opposite outer edges of the base member are beveled as indicated at20 and have a slot 21 formed there in. The slot 21 is relatively narrowto receive the narrow sections 22 of the flexible strap member 23 whichis preferably made of material such as spring steel. The notches 22 arethus placed in the slots 21 and the metal shell is peened over tosecurely hold the spring strap member in place. The notches 22 in theflexible strap will permit the finger members to spring or hingerelative to one another and also permit the abutments to engage, butthey will not permit them to slide relative to each other as the notches22 prevent any relative movement longitudinally of the flexible member23. The ends 24 of the spring member 23 may be projected downwardly toengage the wall of the bore hole and hold the expansion shells inposition until the nut is drawn down sufliciently to expand the fingersand lock the shell member in the hole.

As shown in Figs. 5 and 6 the shell members are provided withcomplementary abutment sections. One abutment is provided with a V orfulcrum trough indicated at 25 and the other is provided with a fulcrummember 26 and when they are placed face to face fulcrum member 26projects within the fulcrum trough 25 and thus forms a flexible jointbetween the two base members. This structure is likewise held by theflexible strap 23 as described in Figs. 1 to 4 inclusive. The spacedabutments in this structure are not permitted to shift laterally orotherwise slip relative to each other.

Referring specifically to Fig. 7 the abutment 30 may extend for the fullwidth of the base member 4 and the slot member 31 may extend clearacross the base members 4. The flexible member 32 can be ofsubstantially the same width and the greater part of the same isreceived within the slot and the material is peened over to hold it inplace. The ends 33 of the spring 32 are flared outwardly to a widerdimension to prevent movement of one shell member relative to the othershell member other than a hinging action.

After the expansion shell members with the nut on the end, of a bolt areplaced in the bore of a hole in the roof of a mine and the nut is drawndown by turning the bolt to. expand the fingers so that their outersurfaces will tightly grip the sides of the hole, the bolt may extend upthrough the shell members and actually push the spring 23 out of itssocket and separate the expanding shell halves. However, under theseconditions the shell halves are themselves locked in position by the nut10 and there is no reason for retaining their relative position to eachother. Any fault in the roof that may occur would ruin the relativeposition of the half members regardless of whether or not they areconnected by a flexible strap. Ordinarily a structure of this type isexpansible and is not removed once it is placed and therefore it is notintended to be used again. For this reason it is not important toconstruct the expansion shell members so that they may be retrieved.

I claim:

An anchor for a mine roof bolt expansion shell having cooperativetapering shell halves with cylindrical hole gripping outer surfaces andopposed flat inner surfaces engaged by a nut threaded on the roof boltand a flexible strap fastened in locking grooves on the small ends ofsaid taperd shell halves which is the hole entering end of the expansionshell characterized in that said locking grooves are on the end faces ofsaid shell halves and said flexible strap is a stiff and straight flatspring having spaced notches in its sides to independently fit in saidlocking grooves to prevent the shell halves from separating at theirsmall tapered ends, the ends of said fiat spring extending laterallyfrom said locking grooves and beyond said shell halves to immediatelyanchor the expansion shell when entered into a hole.

References Cited in the file of this patent UNITED STATES PATENTS606,925 eld July 5, 1898 859,532 Swortfinger July 9, 1907 929,979Pleister Aug. 3, 1909 l,034,607 Frank Aug. 6, 1912 1,076,368 Hubler Oct.21, 1913 1,326,663 Karitzky Dec. 30, 1919 1,702,920 Tomkinson Feb. 19,1929 2,399,069 Skinner Apr. 23, 1946 2,647,431 Lewis Aug. 4, 19532,667,099 Lewis Jan. 26, 1954 2,753,750 Dempsey July 10, 1956 FOREIGNPATENTS 402,375 Great Britain Nov. 30, 1933

